1. Field of the Invention
The present invention relates to an improvement in a small-sized boat thrust by a jet pump.
2. Description of the Related Art
Generally, a small-sized boat often called "Personal Watercraft" is constructed such that a jet pump disposed in an engine room of a hull is driven by a multicylinder engine to thereby thrust the boat. An example of such a small-sized boat is disclosed, for example, in Japanese Patent Laid-Open Publication No. HEI-7-237587 entitled "Water Sliding Boat" in which rotation of an impeller causes water to jet backwardly to thereby thrust the water sliding boat.
The water sliding boat includes a four-cycle two-cylinder engine within a cowling (an engine room) of a hull thereof. The engine drives the impeller. A crankshaft of the engine is disposed along a line passing through a bow and a stern of the hull. Two intake manifolds are connected to the engine such that they extend transversely of the engine. One carburetor is connected to the intake manifolds.
Generally, for improving output characteristics of a four-cycle multicylinder engine, a carburetor is preferably attached to each cylinder. Also, in order to increase a thrusting force of the impeller of the water sliding boat, it is preferable that a plurality of carburetors are connected to the four-cycle two-cylinder engine.
The cylinders have axes inclined obliquely upwardly. In a small space defined between an inner surface of the cowling and side surfaces opposite from inclined sides of the cylinders, there are disposed a carburetor and a cyclone filter. Difficulty is encountered in disposing a plurality of carburetors in such a small space. More particularly, since a float type carburetor has a float chamber, the carburetor provides limited freedom for disposition in the cowling. Further, the carburetor is made relatively large. Moreover, in the case where the float carburetor is employed, a float sways when the hull pitches and rocks. Thus, care should be taken to keep stable output characteristics of the engine.